The present invention pertains to valves and in particular to tri-leaflet heart valve prostheses.
Ever since 1950, when blood oxygenators made open heart surgery feasible, it has been possible to treat some forms of heart disease by replacing one of the patient""s heart valves with a prosthetic valve. Early heart valve prostheses included ball-and-cage valves and disc-and-cage valves in which a ball or a disc was housed in a cage. One side of the cage provided an orifice through which blood flowed either into or out of the heart, depending on the valve being replaced. When blood flowed in a forward direction, the energy of the blood flow forced the ball or disc to the back of the cage allowing blood to flow through the valve. When blood attempted to flow in a reverse direction, or xe2x80x9cregurgitatexe2x80x9d, the energy of the blood flow forced the ball or disc into the orifice in the valve and blocked the flow of blood.
A bi-leaflet valve comprised an annular valve body in which two opposed leaflet occluders were pivotally mounted. The occluders were substantially rigid and moved between a closed position, in which the two leaflets were mated and blocked blood flow in the reverse direction, and an open position, in which the occluders were pivoted away from each other and did not block blood flow in the forward direction. The energy of blood flow caused the occluders to move between their open and closed positions.
A tri-leaflet valve comprised an annular elastic valve body in which three flexible leaflets were mounted to a portion of the valve body, called a xe2x80x9cstent,xe2x80x9d located at the circumference of the annulus. Some tri-leaflet valves used rigid leaflets. When blood flowed in the forward direction, the energy of the blood flow deflected the three leaflets away from the center of the annulus and allowed blood to flow through. When blood flowed in the reverse direction, the three leaflets engaged each other in a coaptive region, occluded the valve body annulus and prevented the flow of blood. The valve leaflets were made from tissue, such as specially treated porcine or bovine pericardial tissue, or from a man-made material such as polyurethane or another biocompatible polymer.
Durability is a desirable characteristic of prosthetic heart valves, including tri-leaflet heart valves, because replacing such a valve is both expensive and dangerous for the patient. Another desirable characteristic of a prosthetic heart valve design is a reduction in thrombus accumulation on the valve.
The invention improves the durability of elastic heart valves by having molded, rather than cut, free edges. This removes the requirement to cut the free edge during the manufacturing process which reduces the likelihood that cracks will develop in the free edge and subsequently cause the valve to fail. Further, by removing the requirement to cut the free edge, the chance of thrombus accumulation on the valve is reduced.
In one aspect, the invention features a valve comprising an elastic valve body, a leaflet having an attachment edge and a free edge, the leaflet being coupled to the valve body on the attachment edge and the free edge of the leaflet having an uncut edge.
Implementations of the invention may include one or more of the following. The valve may further comprise a mold separation point on an inflow face of the leaflet away from the free edge. The free edge may have a full radius. The free edge may comprise a filleted edge.
In another aspect, the invention features an elastic valve body, a leaflet having an attachment edge and a free edge, the leaflet being coupled to the valve body on the attachment edge, and the free edge being molded.
Implementations of the invention may include one or more of the following. The mold separation point may be on an inflow face of the leaflet. The mold separation point may be on the free edge. The mold separation point may be on an outflow face of the leaflet. The leaflet may be molded in a partially open position. The leaflet may be molded in a fully open position.
In another aspect, the invention features a method of manufacturing a valve comprising forming an elastic valve body and a leaflet integral with the valve body, the leaflet having a free edge, the free edge having an uncut edge.
Implementations of the invention may include one or more of the following. Forming may comprise compression molding, injection molding or dip casting. The method may further comprise cutting an opening in the valve, the cutting occurring away from the free edge. Forming may comprise molding the leaflet in a partially open position. Forming may comprise molding the leaflet in a fully open position.